Why does my car battery die in cold weather?

Your car battery dies in cold weather due to a combination of reduced battery capacity and increased power demands from your engine.

Here is what happens under the hood when temperatures drop:

• Slower chemical reactions: A car battery relies on a chemical reaction to generate electrical power. In cold temperatures, this reaction slows down significantly. In fact, a battery can lose up to 60% of its strength in freezing conditions.
• Increased stress and power demand: At the exact moment your battery has less power to give, your engine requires more power to start. Cold weather makes the engine oil thicker and more sluggish. Because the engine is harder to turn over, the starter motor has to draw significantly more power from the battery.

If your battery is already older (typically 3 to 5 years) or partially discharged, the combination of low capacity and high demand is usually enough to prevent the car from starting.